Studies will be conducted to define the mechanisms by which changes in blood volume mediate changes in adrenal corticosteroid secretion. Experiments are designed to identify receptor areas, afferent neural pathways, and organs outside the nervous system involved in the adrenal cortical response to changes in circulatory volume, pressure and flow. The relations among these receptors will be studied, and attention will be directed to temporal and quantitative aspects of the responses to volume changes as well as to the anatomical aspects. The relations among hemodynamic mechanisms controlling adrenal cortical secretion and other mechanisms will be explored.